代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>画三角形</title>
<style>
#trip{
width:0px;
height:0px;
border-top:50px solid white;
border-right:50px solid white;
border-bottom:50px solid green;
border-left:50px solid white;
}
</style>
</head>
<body>
<div id="trip">
</div>
</body>
</html>
效果如图显示: